At the present time skis are primarily manufactured by one of two manufacturing methods: the injection method or the sandwich method. In both these methods the finished product is a ski having an upper belt and a lower belt which are separated by, and affixed to, a core material throughout substantially the entire length of the ski. The belts are usually polymeric laminates, often with fiber-glass reinforcement and preferably have an outer layer of hard cover material, such as polyethylene, which become the top and bottom surfaces of the finished ski. The core material may be wood or a suitable synthetic foam.
In the injection method the upper and lower belts are placed into a mold, and the hollow space remaining between them is filled-in with foam of a suitable synthetic material which adheres to the belts. This method is shown schematically in cross-section in FIG. 1.
In the sandwich method the upper and lower belts are glued under pressure to a cone made of wood or pre-hardened foam, sometimes also providing for air chambers. This mode of construction is shown schematically in cross-section in FIG. 2.
Skis manufactured under either method described above necessarily have the disadvantage of the core material between the upper and lower belts being exposed unprotected in the open at the rear ends of the ski. Since the core materials are softer in case of foams and more brittle in the case of wooden cores mechanical damage often occurs at this juncture and particularly when the skis are positioned upright on the ground. These problems coupled with innate deficiencies of bonded surfaces often results in spliting at the rear end of the ski.
To correct this considerable shortcoming in use, special rear end protectors have been employed up until now; they are either placed into the mold before the filling-in with foam or they are glued or screwed on to the rear end of the ski after proper preparation of the rear end of the ski such as milling-out. In any case, however, such rear end protectors require a separate assembly procedure with either the injection or sandwich methods. By the use of such rear end protectors the problem of durable protection is handled unsatisfactorily, as only a purely mechanical connection exists between the core and the rear end protectors, so that the rear ends of the ski may still be split or wedged apart by bumping or through high stress.